Reel cutting units are well known for use on greensmowers, fairway mowers and other mowers. Such cutting units are designed for precision grass cutting at relatively low heights of cut. Each cutting unit has a frame that mounts a rotatable cutting reel which sweeps grass against a sharpened bedknife to cut the grass. Front and rear rollers carried on the frame allow the cutting unit to roll over the ground. The cutting unit is linked to the mower so as to be propelled by the motion of the mower.
The front roller on a reel cutting unit is often grooved along its length from one end of the roller to the other. Such a grooved roller is often called a Wiehle roller in the mowing art. The rear roller on a reel cutting unit is usually a smooth cylindrical roller without any grooves. While both front and rear rollers are often used on a reel cutting unit to support the cutting unit for rolling, only one roller, i.e. either a front or rear roller, might be used with the other end of the cutting unit being suspended from the mower.
Various ways are known in the art to manufacture grooved rollers of this type. In one method, a roller body is cast as a solid, integral piece. The roller body is then supported by bearings on a through shaft which is fixed to the cutting unit frame. The roller body rotates relative to the through shaft by virtue of the bearings. When the roller body is cast, it is often cast out of iron.
While grooved rollers can be effectively manufactured in this way, there are disadvantages. If the roller body is cast out of iron, it is relatively heavy. U.S. Pat. No. 5,394,681 discloses a cast aluminum roller body which would be lighter than cast iron, but hardness and durability then become an issue. The aluminum roller body disclosed in the 681 patent has to be provided with a hard anodized coating. This takes away some of the advantages of using aluminum in the first place.
Some grooved rollers are known in which the grooved roller body is made from ultra-high molecular weight (UHMW) polyethylene. Such rollers are disclosed in U.S. Pat. Nos. 5,511,365 and 5,829,235. The plastic roller bodies disclosed in these patents are made from a plurality of separately molded, grooved roller body sections that have to be assembled together.
In the 365 patent, a plurality of separate roller body sections are secured to one another in an end-to-end fashion using metallic collars that bridge between adjacent sections. After the roller body sections are so assembled, the roller body is then secured to a through shaft using similar metallic end collars. The end collars are inserted into the ends of the outermost roller body sections. The end collars are then clamped to the through shaft by set screws to secure the plastic roller body to the through shaft.
In the 235 patent, a plurality of roller body sections are stacked end-to-end against each other but do not use bridging metallic collars between adjacent sections as in the 365 patent. Instead, the roller body sections simply interfit or nest with one another. However, end collars are still used to hold the roller body sections together. These collars are clamped to the through shaft by set screws. Thus, in both the 365 and 235 patents, the through shaft is rotatably mounted in bearings carried on the frame of the grass cutting unit—the through shaft is not a fixed shaft.
While the plastic roller bodies disclosed in the 365 and 235 patents provide grooved rollers that are lighter than cast iron roller bodies, they nonetheless are time consuming to manufacture and assemble. Separate roller body sections must be molded. These sections then must be assembled to form the roller body and connectors are often used to do this. Once the sections are assembled, end collars must be secured to each end of the roller body. The roller body must then be clamped to the through shaft. Thus, the manufacturing process is still labor intensive in terms of assembly time and component cost, which raises the costs of manufacturing the grooved roller.
In addition, such rollers may be prone to operational difficulties. They are secured to the through shaft using set screws which may loosen and slip. If this happens, or if any of the various other connectors or fasteners loosen, then the grooved roller may not operate or roll properly. This would require replacement or repair.
Accordingly, there is a need in the art for a roller for use on a grass cutting unit. Such a roller should be strong, durable, and light while being easy and inexpensive to manufacture.